This invention relates to the chemical looping removal of ventilation air methane and has been devised particularly, though not solely, for removing methane from ventilation air in coal mines.
Release of fugitive methane (CH4) emissions from ventilation air in coalmines is a major source of greenhouse gas emissions (the greenhouse impact of methane is 21 times greater than that of CO2). Approximately 64% of methane emissions in coalmine operations are the result of ventilation air methane (VAM). There are two alternative strategies for mitigation of VAM in mining operations, namely: (i) utilisation of VAM as an energy source, (ii) destruction of VAM through an oxidation process. To date, the implementation of the former strategy has found to be difficult primarily because:                the volume of the gas mixture is large (can be as high as 600 m3/s);        the methane concentration in the mixture is dilute (0.1-1% V/V), and;        the concentration of methane and the flow rate of the gas mixture are variable.        
The latter strategy (i.e. VAM destruction) has been found more attractive and easier to adopt. Although technologies based VAM destruction are technically feasible to mitigate VAM when the methane concentration in air exceeds their minimum requirement and economic performance is not an issue, such systems often need additional fuel for continuous operation. Current estimates suggest that the additional fuel intake may be at least 0.9% to maintain methane concentration at suitable levels for prolonged operations. Examples of VAM mitigation systems based on the destruction strategy are:                TFRR (VOCSIDIZER, MEGTEC)        CFRR (CANMET)        CMR, catalytic monolith reactor (CSIRO)        CLBGT, catalytic lean-burn gas turbine (CSIRO, Ingersol-Rand)        RLBGT, recuperative lean-burn gas turbine (EDL)        VAM-RAB, ventilated air methane regenerative after burner (Corkys Pty Ltd)        
The present invention therefore provides an alternative to these earlier forms of VAM destruction by using the concept of chemical looping for mitigation of VAM.